Very little research has been carried out on the impacts of solar farms on biodiversity, despite the proliferation of this industry within the UK.
This study investigates whether solar farms can lead to greater ecological diversity when compared with equivalent undeveloped sites. The research focussed on four key indicators; botany (both grasses and broadleaved plants), invertebrates (specifically butterflies and bumblebees), birds (including notable species and ground nesting birds) and bats, assessing both species diversity and abundance in each case.
A total of 11 solar farms were identified across the southern UK for inclusion in this study. All sites had been completed for at least one growing season. Approaches to land management varied from primarily livestock grazing through to primarily wildlife-focused management. At each site the level of management for wildlife was assessed as low, medium or high based upon activities such as re-seeding, grazing or mowing regimes, use of herbicides and management of hedgerows and field margins.
To assess changes in biodiversity relating to the solar farm, we compared wildlife in the solar farm to wildlife at a “control” plot nearby. The control plot was outside the solar array, but within the same farm. Most importantly, the control plot was under the same management as the solar farm was prior to its construction. The purpose of the control plot was to give an indication of wildlife levels before the solar farm was constructed.
Botanical, invertebrate, bird and bat surveys were then carried out during 2015 on both the solar plot and the adjacent matched control plot. The results of these surveys were compared statistically to identify any changes in biodiversity the solar farm, and its land management, had brought about.
The results of the botanical surveys revealed that over all, solar farms had greater diversity than control plots, and this was especially the case for broadleaved plants. This greater diversity was partly the result of re-seeding of solar farms: where species-rich wild flower mixes had been sown this diversity was greater, but even where agricultural grass mixes had been used diversity was greater as compared to the largely arable control plots.
Management of grassland also influenced botanical diversity. At sites with conservation grazing (winter and spring sheep grazing with a pause through the summer for wild flowers to flower and set seed), plant diversity had increased through natural processes as compared to the original seed mix.
The invertebrate surveys revealed that butterflies and bumblebees were in greater abundance on solar farms than on control plots, and the greatest numbers occurred where botanical diversity was also high. The number of species did not differ significantly between most solar farms and control plots. However, at several sites with higher botanical diversity, and where management for wildlife was considered to be ‘high’, a greater diversity of bumblebee and butterfly species was observed.
The bird surveys revealed that over all, a greater diversity of birds was found within solar plots when compared with control plots. On two of the sites, a greater abundance of birds was observed on the solar farms when compared with control plots. The greater abundance and species of birds on these sites suggests foraging opportunities within the solar farms are greater than on the adjacent undeveloped sites.